A motor vehicle system, for example a braking or steering system, which is suitable for automatic operation requires a redundant power supply, i.e. a power supply delivered by two on-board networks, such that the operation of a system or a plurality of systems can be maintained, even in case of faults or outages (functional security). Internal redundancy in respect of actuator technology and power electronics is also required.
From DE 19960611 A1, an electromechanical braking system is known, having a generic brushless DC motor for two independent on-board networks with an identical voltage level of 2×12 V, in which the stator winding is sub-divided into at least two separate windings with respectively equal numbers of turns, such that each part of the stator winding can be connected to one of said on-board networks via a respective power electronics circuit. By this subdivision of the stator winding according to the number of independent on-board networks in a vehicle, a plurality of mutually-independent half-motors are formed such that, in case of the failure of one of the two on-board systems, a half-motor can continue to operate using the other on-board network, with reduced output power.
In a brushless DC motor of this type according to DE 19960611 A1, subdivision of the stator winding is achieved by means of taps on the continuous winding. However, the voltage supplies are required to operate at different levels. As a result of the lack of mechanical separation of the coil windings associated with the two on-board networks, however, potential faults affecting the control thereof cannot be excluded, such that genuine redundancy is not achieved.
The divided stator windings provided for the two on-board networks are configured as separate windings, which are mutually overwound or interwound, wherein, for each of these separate windings, an output stage is provided, with six circuit-breakers. By overwinding or interwinding, however, a short-circuit associated with the contact of wires, which would affect both half-motors and compromise the availability thereof, cannot be ruled out. To date, it has consistently been required that, insofar as possible, both half-motors should perform identically and, accordingly, are operated using two output stages of identical design and substantially identical controllers. Moreover, for future applications, on-board systems with higher rated voltages than the customarily-applied 12 V or 14 V are envisaged for which, in many cases, no redundancy is to be provided.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.